Drier



L. R. CHRISTIE DRIER May 26, 1925.

Filed July 5, 1923 4 Sheets-Sh et 1 INVENTOR May-26, 1925.

I L. R. CHRISTIE Filed July 3; 1923 4 Sheets-Sheet 2 May 26, 1925.

L. R. CHRISTIE DRIER Filed July 5, 1923 4 Sheets-Sheet 3 i it; 46

4 Sheets-Sheet 4 INVE NTOR 42. 4;

May 26, 1925' L. R. CHRISTIE DRIER Filed July 1923 Patented Nlay 26, 1925.

UNITED STATES LINDSAY R. CHRISTIE, OP PITTSBURGH, PENNSYLVANIA, ABSIGNOBTO DUFF PATENTS COMPANY, INCORPORATED, OF PITTSBURGH,

PORATION OF PENNSYLVANIA.

PENNSYLVANIA, A COR- DRIER.

Application filed July 8,

To all whom it may concern:

Be it known that I, LINDSAY R. Cnars'rin, a citizen of the UnitedStates, residin at Pittsburgh, county of Allegheny, and tate 5 ofPennsylvania, have invented a new and useful Improvement in Driers, ofwhich the following is a full, clear, and exact description.

The present invention relates to driers, and more particularly toindirect heat driers for use in drying powdered and granular or clazyeymaterial. I n object of the present invention is the provision of .adrier of the general type disclosed in my Patent No. 1,318,133 ofOctober 7, 1919, but embodying means insuring a substantially dustlessoperation of the drier. To that end, a feature of the invention is theprovision of a drier comprising a rotary drum for receiving the materialto be dried, means for withdrawing evaporated moisture from said drum,and means associated with the intake and discharge openings of the drumfor substantially preventingv the ingress of air through said openings,whereby said moisture is removed from said drum substantially free ofdust.

It has heretofore been proposed in the art to which this inventionrelates to provide a cylindrical drum having heat ducts passingtransversely therethrough and opening through the cylindrical outershell of the drum. said ducts dividing the drum into a plurality ofdryingcompartments extending longitudinally thereof, and the cylindricalshell into a plurality of separate parts, the construction beingsomewhat similar to a bundle of parallel tubes connected at their I endsto headers. An objection to a structure of this kind is that, due to thedivision of the outer shell of the drum into a plurality of separateparts, the capacity of the drum to withstand the torsional strains setup therein in driving the same is greatly impaired. By the presentinvention, I have avoided this objectionable feature in a drier of thisgeneral type by forming the cylindrical shell continuous and imperforatearound at least a substantial'longitudinal 59 section of the drum,preferably a centrally located section thereof.

Another object of the present invention is to provide a rotary drumhaving a plurality of drying compartments separated by a plu- 1923.Serial in. 849,206.

, rality of heat ducts, the drum being so constructed that substantiallyall portions of the walls thereof exposed to the direct action of thehot gases are protected by the material being dried, thereby avoidingdanger of burning the plates.

Whereas it has heretofore been proposed to divide the rotary drum intofour longitudinally extending tubes or compartments of substantiallyequal cross-sectional areas and radiating from the center of the drum,it is sometimes desirable to increase the number of such compartments inorder to obtain a greater heating surface and a better heat penetrationof the material being dried. By dividing the drum into more than fourcompartments, however, all radiating from the center of the drum, anacute angle is formed between the radial sides of at least some of thecompartments, which is objectionable on account of the tendency of thematerial to stick to the sides of the compartments in such angles. Afurther object of the present invention, therefore, is to provide a drumwhich may embody any desired number of compartments, each having everyangle between its walls substantially a right angle or greater than aright angle.

Still another object of the invention is to so design the compartmentsinto which the drum may be divided, irrespective of the number andvarying sizes of such compartments, that the lengths of the arcs whichthe a various compartments subtend on the outer shell of the drum shallbe proportional'to the total amounts of heating surfaces of suchcompartments.

In the accompanying drawings, there is shown, for purposes ofillustration only, one embodiment of the present invention, it beingunderstood that the drawings do not define the limits of the invention,as changes may be made in the construction and operation thereindisclosed without departing from the spirit of the invention or scope ofmy broader claims.

In the drawings:

Figure 1 is a central vertical longitudinal sectional view through adrier constructed in accordance with my invention, and showing therotary drum partly in section and partly in elevation;

Figure 2 is a transverse vertical sectional view on the line II-'II ofFigure 1:

' drier comprises a rotary drum A enclosed in a suitable housing B whichmay be connected with a furnace C for supplying hot gases.

The drum A is supported adjacent its opposite ends for rotation uponrollers 2 engaging tracks 3 on the drum, and is rotated by any suitablemeans, such as a pimon 4 engaging a gear 5 on the drum A, the pinion 4being mounted u on a shaft 6 which carries a belt pulley Referring to-Figure 1, it will be seen that the drum A comprises a cylindricalsection 8 at the intake end and a cylindrical section 9 at the dischargeend thereof. The main body portion of the drum, intermediate the endsections 8 and 9, as shown in Figures 2, 3 and 5, is divided into fourdrying compartments or tubes 10 by radial heat ducts 11. The tubes orcompartments 10 extend longitudinally of the said body portion of thedrum and open at their opposite ends into the cylindrical sections 8 and9. The heat ducts 11 alsgextend longitudinally of said body portion, butare closed at their opposite ends by artition plates 12 between the endsof the ody portion of the drum and the end sections 8 and 9. The radialarms of these partition plates are channelshaped in cross section for apurpose to be brought out hereinafter.

The body portion of the drum is preferably divided longitudinally intothree sections of. substantially equal lengths. The radial heat ducts 11open through the outer cylindrical shell 13 of the body portion in theend sections thereof, as shown in Figure 5, thereby providing for thepassage of the hot gases transversely through said end sections, but inthe middle section of said body portion, these radial ducts are closedat their radial outer ends, and the shell 13 is continuous andimperforate around this middle section of the drum. This constructionenables the drum to better withstand the torsional strains set up in thesame when it is rotated, than if the radial ducts 11 opened through theouter shell 13 throughout the length of the body portion of the drum,and thus divided said outer shell into a plurality of parts separatedfrom each other throughout the length of the body portion.

Referringto Figure 3, it will be seen that the outer radial ends of theheat ducts 11in the middle section of the body portion of the drum areclosed by bending inwardly the outer radial edge portion of one sidewall of each duct to engage the other side wall thereof, and rivetingthese walls together. By reason of this construction, the wet materialin the tubes 10 is enabled to contact with substantially the entireinner surface of the outer shell 13 of the drum, and thereby protect thesame from being burned out by the hot gases, whereas if both side wallsof each radial duct 11 were extended straight out to the outer shell 13and riveted thereto in the middle section of the body portion, in thesame manner as in the end sections of said body portion, portions of theouter shell 13 would be subjected to the action of the hot gases both onthe inner and outer surfaces thereof, and would be liable to be burnedout. Communication between the radial ducts 11 of the end sections ofthe drum and the compartments 10 is prevented at the middle section ofthe drum by plates 31 shown in Figures 2 and 5.

It will be noted that the manner of clos-- ing the outer radial ends ofthe ducts 11, as illustrated in Fi ure 3, provides a space or pocketbetween t e outer closed end of each duct and the cylindrical shell forthe wet material to lodge in. The purpose of the channel formation ofthe channel plates 12 is to enable these plates to maintain a layer ofwet material in the channels thereof to protect said plates from beingburned out by the hot gases passing through the ducts 11. a

The material to be dried is introduced into the end compartment 8through a tube 14 extending through an intak opening 15 in the end wallof the drum. ositioned in the tube 14 is a feed screw 16 which carrieson its outer end a belt pulley 17-, whereby the screw may be driven fromany suitable source of power. into the end compartment 8 is conveyed byhelical flights 18 therein to the several drying compartments 10. Thematerial in the compartment 8 being divided at the en. trance to thecompartments 10, does not mix again until it has passed through the heatzone, when it falls into the discharge end compartment 9 land is tumbledabout and mixed again by cascading flights 19 in said end compartment.Secured to the discharge end Wall of the drum are a plurality of buckets20 arranged to receive the material and having inclined flanges 21extending. through a discharge opening 22 in said end wall. Thedischarge 0 ening 22 is in communication with a ischarge chute 23.Arranged in said discharge chute is a rotary gate valve 24 havingassociated therewith a belt pulley 25, whereby said valve may berotated. In order to produce a desirable cascading effect within thecompartments 10,

The material introduced I any given temperature.

suitable studs 26 may be provided, said studs projecting from the wallsof said compartments.

The evaporated moisture is withdrawn from the drum by a'small fan 27located at the feed end thereof, and communicating with the intakeopening 15 by a pipe 28. This fan is designed to have over capacity torthe moisture evaporated, thereby creating a partial vacuum within thedrying drum.

The provision of the feed screw for feeding the material through theintake opening and the gate valve associated with the discharge opening,substantially prevents ingressoi air into the drum, so that the moistureis withdrawn substantially free of dust. The vacuum maintained in thedrum is very sli ht, and the velocity of the evaporated moisture is notgreat enough to carry out any dust. This vacuum is very desir able, asthe rate of evaporation increases with each pressure decrease, andthereby insures more rapid drying of the material at Moreover, thegreatest volume of steam produced is at the intake end where thematerial is not dusty, and tapers off to substantially nothing at thedischarge end. \Vhile I have disclosed a feed screw and a rotary valveassociated with the intake and discharge openings for preventing theingress of air into the drum, it will be understood that any otherequivalent means may be utilized for this purpose, and I therefore donot limit myself to the use of the particular means disclosed.

In Figures 1, 2, 3 and 5, I have shown a drum divided into four dryingcompart ments separated by four radial heat ducts, audit will be notedthat in this construction every angle between sidewalls of the variousdrying compartments is substantially a right angle. It is sometimesdesirable to divide the interior of the drum into more than four dryingcompartments, but if all such compartments radiated from the center ofthe drum, the angle formed between the" radial side walls of eachcompartment would be an acute an le, which would be objectionablebecause 0 the tendencyof the material to cling to such walls in theangle therebetween. In Figure 7 I have shown a modified construction inwhich the interior of the drum is divided into eight drying compartments10' separated by radial heat ducts 11', and it will be noted that everyangle between side walls of every stantially equal drying, so that whenthe 1 material has passed through these compartments and again is mixedtogether in the discharge compartment, the entire mass will be uniformlydried.

The operation of my improved drier is substantially as follows: Hotgases generated in the furnace C pass from the furnace around the entirelength of the outer shell of the body portion of the drum A, and alsothrough the heat ducts which extend transversely through the endsections and longitudinally of the middle section of said body portion.These gases, after having given up the greater part of their heat, areexhausted by means of a fan 29 located adjacent the discharge end of thedrum and communicating withthe housing B through an opening 30 therein.The material to be dried is fed into the intake end compartment 8 by thefeed screw 16 and is conveyed by the cascading flights 18 into theseveral compartments 10, through which it passes and is finallydischarged into the discharge end compartment 9, from which 'is passesthrough the opening 22- into the discharge chute 23 and past the gatevalve 24. The drying is done entirely by the indirect ap plication ofheat, and the evaporated moisture is withdrawn in a substantiallydustless condition by the fan 27 It will be obvious that, if desired,inert gases may be introduced into the drum, the sealing of the drumretaining these gases and preventing their contamination.

An important advantage of the present invention arises from theprovision of :1 drier of the indirect heat type having means forwithdrawing the evaporated moisture in a substantially dustlesscondition.

Another advantage of the invention arises from the provision of a rotarydrum so constructed that substantially all portions of the walls thereofwhich are subjected to the direct action of the heating medium areprotected against burning by the material being dried.

A further advantage of the invention arises from the provision of arotary drum having a plurality of drying compartments separated fromeach other by a plurality of heat ducts, and in which the outer shell ofthe drum is continuous and imperforate throughout a substantiallongitudinal middle section'of the drum.

A still furtherv advantage of the invention arises from the provision ofa. drum having a novel arrangement of drying compartments and heatducts, whereby the interior ment having inta of said housing, and meansassociated with of the drum may be divided into any desired number ofsuch compartments, and all of the angles between the walls of theseveral compartments maintained at least as great as a right angle.

I claim: 1. In a drier, a rotatable drum having a compartment forreceiving material to be dried, a housing surroun ing said drum, meansfor rotating said drum, said compartze and discharge openings thereinand an outlet for, thewithdrawal of evaporated moisture but beingotherwise closed to the ingress of outside air, means for withdrawingevaporated moisture from said drum through said outlet, means forsupplying a heating medium to the interior said openings forsubstantially preventing the ingress of air therethrough, whereby saidmoisture is removed from said drum substantially free of dust,substantially as described.

2. In a drier, a rotatable drum having a compartment for receivingmaterial to be dried, a housing surrounding said drum, means forrotating said drum, said compartment having intake and dischargeopenings therein and an outlet for the withdrawal of evaporated moisturebut being otherwise closed to the ingress of outside air, means forwithdrawing evaporatedmoisture from said drum through said outlet, meansassociated with said openings for substantially preventing the ingressof air therethrough, whereby said moisture is removed from said drumsubstantially free of dust, said drum having heat ducts therein, andmeans for supplying a heating medium to the interior of said housing,substantially as described.

3. In a drier, a rotatable drum for receiving material to be dried, theouter shell of said drum being continuous and imperiorate throughout asubstantial longitudinal section of said drum, and a heat duct extendingthrough said section, said shell having openings therein adjacent theopposite ends of such imperforate portion with which said ductcommunicates, substantially as described.

' 4. In a drier, a rotatable drum for receiving material to be dried,the outer shell of said drumibeing continuous and imperforate throughouta substantial longitudinal middle section of said drum, and a heat ductextending through said'section, said shell having openings thereinadjacent the opposite ends of such imperforate portion with which saidduct communicates, substantially as described.

5. In a drier, a rotatable drum for receiving material to be dried,said. drum having its interior throughout the greater portion of itslength divided into a plurality of drying compartments extendinglongitudinally of the drum and separated from each other by a pluralityof heat ducts openin through the outer shell of the drum, said s ellbeing continuous and imperforate throu hout a substantial longitudinalsection of sai drum s aced a substantial distance from both ends tereof, substantially as described.

6. In a drier, a rotatable drum forv receiving material to be dried,said drum comprising a single'compartment at each end therethrough theouter shell of the latter, sub-- stantially as described.

7. In a drier, a rotatable drum for receiv-' ing material to be dried,said drum comprising a single com artment at each end thereof, and aplurality of drying com artments extending longitudinally of the drumand communicating at their 0 posite ends with said end compartments,said drying compartments beingseparated from each other by a pluralityof heat ducts extending transversely through the drum and openingthrough the outer shell of the latter, said outer shell being continuousand imper'forate throughout a substantial longitudinal section of thedrumspaced a .substantial distance from both ends of the latter,substantially as described.

8. In a drier, a rotatable drum for receiving material to be dried, saiddrum comprising a single compartment at each end thereof, and aplurality of drying compartments extending longitudinally of the drumand communicating at their opposite ends with said end compartments,said drying compartments being separated from each other by a pluralityof heat ducts substantially coextensive in length with said dryingcompartments and extending transversely through the drum and openingthrough the outer shell of the latter, substantially as described.

9. In a drier, a rotatable drum for receiving material to be dried, saiddrum comprisy a plurality of heat ducts substantially coextensive inlength with said drying com partments and extending transversely throughthe drum and opening through the outer'shell of the latter, said outershell bepartments being separated from each other ing continuous andimperforate throughout I a substantial longitudinal middle sectionthereof. substantially as described.

10. In a drier, a rotatable drum for receiving material to be dried,said drum having a plurality of radial heat ducts opening through theouter shell thereof permitting1 hot gases to pass transversely throughsai drum, and a plurality of heat ducts branching off from said radialducts and also opening through said outer shell said ducts dividing theinterior of said drum into a plurality of drying compartments, theconstruction being such that the angles formed between the walls of theseveral compartments are all at least substantially as great as a rightangle, substantially as described.

11. In a drier, a rotatable drum for receiving material to be dried,said drum having its interior divided into a plurality of dryingcompartments radiating from the center thereof and separated from eachother by radial heat ducts,and a plurality of compartments interposedbetween said radial compartments and separated therefrom by radial heatducts, each of said compartments having one of its walls formed by aportion of the outer shell of the drum, the lengths of the arcs on thecircumference of the outer shell subtended by the several compartmentsbeing proportional to the total heating surfaces of said compartments,substantially as described.

In testimony whereof Ihave hereunto set my hand.

LINDSAY R. CHRISTIE.

